The present invention is concerned with a jet propulsion engine assembly for aircraft mounted within a longitudinal pod or nacelle housing. It is chiefly concerned with the enclosure in such housing having an open air intake nose and an openable tail end which preferably permits selective exhaust out of the latter from a plurality of operating jet propulsion engines housed therein.
In the prior art it has been proposed in the United States Griffith Pat. No. 3,153,907 of Oct. 27, 1964 to mount concentrically in a tubular outer casing a central tubular engine pod in which is clustered about the central axis of the latter a pair of diametrically spaced and longitudinally extending gas turbine engines. Longitudinal shafts of these engines are geared to a central longitudinal air impeller shaft downstream of the exhausts of the turbines of the pair of engines and within the gas flows from the latter to hazard heat injury to the gearing. These engines drive in opposite directions through such gearing a pair of coaxial fans within the tubular outer casing to force air rearward through the latter into which the engine exhaust gases flow. Such gaseous mixture is ultimately exhausted downwardly through openings in elongated zones of the bottom of the fuselage to provide some vertical lift. Accordingly, these proposals are not pertinent to the subjects matter claimed herein.
It is a general object of the present invention efficiently to embody in a longitudinal tubular housing having an open air intake nose, a typically conventional type of airflow impeller which may be of the compressor or fan blade types, or other obvious variants thereof, with the rotary blades of the impeller carried by a longitudinal central shaft driven from a central jet engine mounted within the housing having its longitudinal shaft aligned with the impeller shaft and drivably connected thereto by disengagable clutching means for drive of the impeller shaft by this engine when operating. This generic embodiment includes a plurality of flanking jet engines which respectively have drivable longitudinal shafts and are arranged annularly about the central engine at substantially equal radial angles apart with their shafts also drivably connected to the impeller shaft by independent disengagable clutching means so that each of the engines may be selectively disengaged from the impeller shaft upon inoperability of any of such engines. The drive shaft of each of the engines of this generic embodiment has associated therewith upstream of this engine and downstream of the impeller an individual cooperative upstream airflow door means so as appreciably to close off airflow from the impeller back through the housing space of this particular engine upon termination of combustion in the latter.
The jet power plants or engines proposed herein for employment in various embodiments of the present invention may be of a variety of types, e.g., turbojets, fanjets, and variations thereof. By way of example the present disclosure proposes the use of jet engines of the gas turbine type with the longitudinal shaft of each such engine being driven by its turbine.
When embodiments of the invention include the basic combinations of units or subassemblies indicated above it is important that the upstream doors of each jet engine are embodied to cooperate with the longitudinal shaft thereof for substantially closing off flow of pressurized air from the impeller back through the interior of such an engine when it becomes inoperative, such as by flame-out. However, although it may be desirable also to provide the downstream tail pipe exhaust opening of each of the engines with suitable closing doors, perhaps as a protective measure or stream lining function, this is not an essential feature.
It is desirable to provide engines of embodiments of the invention with air bleed-off systems to reduce the intake to thrust ratio when one or more of the engines is or are inoperable so that performance of the operating engines is not hampered.
Another object of the invention is to make provision for reducing the ratio of air intake into the tubular housing or nacelle in which the group of engines are mounted and operated to the thrust produced by the operating engines when one or more of the group are inoperable, so that performance of the operating engines is not undesirably hampered. In accordance with a feature of the present invention this may be accomplished satisfactorily by a selective air bleed-off system intervening the air impeller and the air intakes of the engines. Advantageously and uniquely this may be attained by incorporating with the upstream airflow door means of each of the flanking engines provision for bleeding off impeller-supplied pressurized air when the particular door means that is associated with a certain such engine that becomes inoperable is manipulated to closure of the upstream air intake of this particular engine. Such air bleeding-off means may include provision for directing such pressurized air at such door means to and out through an air escape outlet having direct communication with the atmosphere and which is operatively effective only upon closure of the upstream door means of this engine. More specifically, such certain door means may have a manipulative section which in one position closes this associated air escape outlet with simultaneous opening of the flow passage from the impeller back through the particular flanking engine, and vice versa.
An additional object of the invention is to provide advantageously such impeller-supplied air escape equipment with manipulative fairing means which will close off and cover advantageously the exterior escape outlet when the upstream airflow door means of a particular operating flanking engine is open to satisfy the air demand of this engine.
It may be desirable for some services to take advantage of the secondary thrust created by the impeller pressurized air at the rear of the tubular housing as it bypasses the flanking engines and the central engine, for supplementing the thrust of the combustion gases exiting from the tail pipes of the operating engines, such as in a fanjet type engine. The more the flanking engines which are clustered about the central engine, within the longitudinal tubular housing or nacelle, the lesser will be the flow through spaces at the open tail end of the housing. Other services may demand that such intervening spaces between the tail pipes of the engines and also between them and the nacelle housing be closed off by fairing skin of the housing which may be smoothly tapered from the open front end section back to the thrust nozzles provided by the open downstream ends of the tail pipes, such as in a turbojet type engine.
If thrust reversers are required for such an engine assembly, as may be the case for power plants of airliners, they readily may be installed and used without undue interference with the structures embodying features of the present invention and the functions of the latter. The functions of such thrust reversers may be embodied in downstream door means which may desirably function as closing doors when desired.